Hungary was part of the polyglot Austro-Hungarian Empire, which collapsed in World War I. It fell under communist rule following World War II. A revolt in 1956 and an announced withdrawal from the Warsaw Pact was met with massive military intervention by Moscow. In the more open GORBACHEV years, Hungary led the movement to dissolve the Warsaw Pact and steadily shifted toward multiparty democracy and a market-oriented economy. Following the collapse of the USSR in 1991, Hungary developed close political and economic ties to Western Europe. It joined NATO in 1999 and is a frontrunner in a future expansion of the EU.